The lithium-sulfuryl chloride (Li/SO.sub.2 Cl.sub.2) cell has been a subject of research and development investigation for the last ten years because of its potentiality for high voltage and capacity as an ambient temperature primary cell with improved safety characteristics. This system, with its high gravimetric and volumetric energy density is a desireable power source for military applications requiring high energy density, extremely long shelf life and/or discharge time and are being tested presently for such applications.
The cell basically is comprised of a lithium foil anode, a coducting SO.sub.2 Cl.sub.2 electrolyte solution as for example 1.5M LiAlCl.sub.4 --SO.sub.2 Cl.sub.2 and an inert porous carbon based cathode fabricated by bonding carbon black powder to a support nickel matrix using about 5 to 10 percent of Teflon as the binding agent.
Cathodes for other lithium battery systems such as lithium thionyl chloride (Li/SOCl.sub.2) are normally formulated with Shawinigan acetylene carbon black, a low surface area carbon black of 60 m.sup.2 /g, and achieve satisfactory performance. However, similarly constructed cathodes when studied in Li/SO.sub.2 Cl.sub.2 cells produce rather discouraging results in terms of reduced operating voltages and capacities.
In Li/SO.sub.2 Cl.sub.2 cells, overall cell operating life in both room temperature and low temperature applications is primarily limited by the reduction process occuring at the Teflon bonded carbon cathode. The carbon cathode must accommodate LiCl formed during cell discharge while allowing continued transport of cathode reactants and conducting ions. When the cathode becomes clogged by LiCl deposits, it can no longer allow sufficient transport of ions and it polarizes severely thereby reducing effective operating cell voltage and causing premature cell failure. There is yet another particularly interesting feature of the Li/SO.sub.2 Cl.sub.2 system. Sulfuryl chloride undergoes a thermally activated catalytic decomposition to yield SO.sub.2 and Cl.sub.2, both of which are soluble in SO.sub.2 Cl.sub.2. However, since molecular Cl.sub.2 is more reactive than the undissociated parent SO.sub.2 Cl.sub.2, it operates at higher potentials thereby contributing to increased operating voltage.
Since carbon is a well known catalyst for the above reaction, high electrode surface area is important in terms of achieving high operating cell voltages.
However, mixability and wettability of high area carbon blacks with water and a suitable Teflon binder such as Teflon 30 is not particularly good. The resulting cathodes formed are not structurally sound and tend to crumble rather easily under mechanical shock. Because of these problems, state of the art cathodes for these cells have been constructed with low surface area carbon blacks that produce cathodes of good mechanical adhesion and structural rigidity although with substantially reduced catalytic activity. The resulting poorer voltage performance in cells constructed with these low area carbon blacks has necessitated doping the cathodes or electrolyte solution with additions of such materials as Cl.sub.2, expensive conducting precious metal catalysts such as platinum, addition of heterogeneous and homogeneous electrocatalysts in the form of transition metal complexes of macrocyclic compounds such as cobalt and iron tetraazaannulenes and cobalt and iron phthalocyanines. Long term stability or safety implications of these additives in full cells have yet to be investigated.